The effect of short-term food deprivation and re-feeding on the resistance of juvenile Caspian roach, Rutilus caspicus to the salinity of the Caspian Sea: growth performance, stress indices and immune response

This study was performed to evaluate the ability of juvenile Caspian roach Rutilus caspicus (1.4 ± 0.018 g) to acclimate to the salinity of the Caspian Sea by the direct transfer method with short-term starvation and re-feeding periods within 60 days. So, 450 juvenile fish were randomly distributed into 5 groups: three groups were deprived from feeding for 3, 5 and 7 days (3S, 5S and 7S). They were then re-fed for 10 days and this cycle was repeated during 46 days. Forth group were unfed during the whole experimental period (S) and fifth group were continuously fed (F or control group). All fish after the starvation-refeeding in freshwater were directly transferred to the Caspian Sea water for 14 days, and staved during this period. Growth performance were evaluated for all of the experimental treatments. Some of stress indices (osmolality, cortisol and glucose) and immune response (total immunoglobulin and lysozyme) concerning to the alternative nutritional periods and abrupt salinity elevation were measured in fish blood. The highest and lowest fish growth performance were obtained in F and S groups, respectively. Osmolality and lysozyme activity were not statistically significant between F, 3S and 5S groups. Total immunoglobulin was significantly increased in 5S (31.50 ± 0.99 mg/g). The highest cortisol and glucose concentrations were obtained in groups 7S and S compared to the other experimental groups. The results showed that, not only the juvenile roach with the short-term feed deprivation periods in 3S and 5S groups were not affected by physiological stress due to starvation and increased salinity, but also their growth performance enhanced because of living in iso-osmotic environment of the Caspian Sea.